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PHOENIX -- Arizona’s medical marijuana laws and traffic laws could be headed for a collision, and drawn-out court battles could be on the horizon. This on the eve of the opening of the state’s first medical marijuana dispensary in Glendale.

“There’s a lot of people that could test positive for marijuana after going to a dispensary that are now opening and they will leave there after having stayed an hour, taken their medical marijuana, and be perfectly fine to drive but test positive,” said Brent Kleinman, an attorney at the Kleinman Law firm.

Arizona has a zero-tolerance policy when it comes to using pot and driving.

“If there’s any trace of it whatsoever, that’s grounds for a DUI charge,” said Kleinman.

Kleinman said because the drug can stay in a person’s system for weeks, it is feasible that a medical marijuana user could be safe to drive, but still be charged.

There are currently more than 500 law enforcement officers in the state specially trained to determine whether a driver is under the influence of drugs.

“We’re probably the top state in the union when it comes to making sure our officers are trained,” said Alberto Gutier of the Governor’s Office of Highway Safety, the department that runs the Drug Evaluation and Classification program.

Gutier said he does not think it is likely a medical marijuana user could use the drug and get a DUI three days later. He said a person would have to show obvious signs of impairment that officers have been trained to detect.

“The officer will come in, talk to the person that is driving, ask him some questions to establish probable cause that he is impaired,” he said.

Officers will also perform a field sobriety test, and if necessary take a suspected impaired driver for a blood test.

If that test shows any sign of marijuana, Gutier says, “They’re going to be arrested. Period.”

Kleinman believes that is precisely the reason Arizona’s courts will become back-logged with marijuana related cases once the dispensaries start to open.

“I think you need to have a benchmark, especially with medical marijuana being allowed," Kleinman said.

Washington state legalized marijuana in last week’s election, and also changed their DUI law by setting a new blood-test limit for the drug, similar to a blood-alcohol level.

That would mean that a person would have to have a certain amount of the drug in their system before they could be charged with a DUI.

Arizona has no such law. Any amount is too much, even if a person has a prescription.